To investigate the cause of scatter and deviation of knockdown factor, which is defined the ratio of experimental buckling load and theoretical buckling load, buckling test of CFRP (Carbon Fiber Reinforced Plastics) cylindrical shells was conducted. Because CFRP is lighter, higher strength and stiffness than metallic materials, it is used for cylindrical shells of satellites, aircraft, and rockets. For lightweight design, the cylindrical shell is required to be thinner, but buckling tend to occurs. Thus to investigate the cause of scatter and deviation of knockdown factor is important for lightweight design. It is said that the cause of knockdown factor is mainly shape imperfection, however, the shape imperfection cannot explain the knockdown factor. Hence the buckling test of CFRP cylindrical shells focusing on ply-gap, ply-overlap, which is typical problem of composite material manufacturing, was performed. In addition, to improve the prediction accuracy of the buckling load, the elastic moduli of cylindrical specimen were measured by tensile and compression tests. Moreover, effect of length to radius ratios, offset of the center of cylinders to the center of load, and thickness of strain gage which had not been focused on previously were also investigated.
